Electrical – Locating source of excessive energy use

electricalenergyenergy efficiency

Background Info: My house is all electric.

Last month when I got my electric bill, I flipped. It was triple that of any month prior. Now I know the cold (heating) can affect this so I decided to turn my thermostat back, even though I never had to before. I've finally got the results back and to my surprise, it's still pretty darn high (but somewhat lower thankfully). The head-scratcher is that not only did I turn my thermostat down 4-6 degrees, it also hasn't been very cold here lately. It has ran a fraction of what it did the month prior, and that's just from the ambient temp difference. This isn't considering the fact that the thermostat is off for half of the day while I'm at work. I also wouldn't deem my system extremely inefficient, as I have a heat pump.

Anyways, so I'm suspecting there's something else at play here. Perhaps another large appliance like the washer/dryer, dishwasher, hot water heater, etc. However, I do not know how to troubleshoot this or determine how much energy any one appliance is using.

Are there any pro-tips or easy/cheap ways that I can measure, or at least get a general idea, of which appliance in my house could be causing such high energy usage? I've seen before meters that you plug into the wall (in-between the socket and appliance), but I imagine those are not the most inexpensive route to take. I was wondering if maybe I could see the real-time load for the entire house? Like at the meter, and then I could one-by-one disconnect appliances and notate the fluctuations in total usage.

Anything like that would be great, or if you have better ideas, please share!

Quick Note: I recently had someone move into one of my spare rooms. One of my suspicions that I'm looking to verify is that they take extra long showers and overwork my hot water heater. I mainly suspect this because they mentioned that they ran out of hot water, something that has never happened to me before.

I wouldn't be concerned if I was still considered "efficient" by my electric company, but as you can see, I went from being relatively efficient to not even close.

UPDATE 3/3/2018 After doing some testing, I've come to realize that my heat pump isn't putting out any heat at all. So basically, I have been running off AUX heat exclusively. That combined with how cold it has been may very well explain the large spike in usage. I called a tech to come look at it. I will update and close this question once it has been verified.

UPDATE 12/10/2018 It has been a while so I thought I would share with everyone what the real issue was. After a few visits, it was finally discovered that my heat coils were stuck on. Even with the thermostat off, they were getting constant power. You could actually feel the heat radiating from the floor above the coils (they're in a crawl space). I'm lucky they found it, otherwise I could've had a fire on my hands. So yes, in essence, my AUX heat was running 24/7 for what was likely a month or two. CRAZY!

Best Answer

Since you say your backup heat is electric, I'd say that's what is using all the power. It could be that the weather is unseasonably cold and that the backup emergency heat is kicking in often.

Your Nest Thermostat could be switching to AUX heat more often than your old thermostat would have.

Since you say your nest thermostat is new (last summer), It is likely that it is responsible for kicking on the aux (emergency) electric heat more often than your old thermostat. There are settings to change how often this happens described below.

Your Nest thermostat may calling for aux heat more often than your old one would have. This can be configured with Heat Pump Balance which you might try changing to Max Savings or balanced. Note that the link below states that Max Comfort, the most expensive option, is selected by default. This is probably the issue. If changing this doesn't help, then I'd call an HVAC specialist.

Because auxiliary heat is so expensive, running the heat pump longer is still cheaper than using AUX heat. Heat Pump Balance automatically turns the heat on early to reduce AUX heat use as much as possible and get to your target temperature on time. It can turn on the heat up to 5 hours before a scheduled temperature if necessary. So if your schedule says 70ºF/20ºC at 7pm, Heat Pump Balance can use Early-On technology to start heating as early as 2pm.

Heat Pump Balance gives you four options to choose from:

Max Savings - This is the best setting for saving energy. In Max Savings mode, the Nest thermostat gives the heat pump more time to get to your target temperature before turning on AUX and sets a lower AUX lockout temp.

Balanced - This setting will give the heat pump more time to work, but will still turn AUX on quickly if it looks like it won't get you to your target temperature on time. Balanced has an AUX lockout temp somewhere between Max Comfort and Max Savings.

Max Comfort - When you choose Max Comfort, the Nest thermostat will make sure you'll get to the temperature you want, even if it means using auxiliary heat. Max Comfort is the default setting for Heat Pump Balance and generally gives you a higher AUX lockout temp.

Off - You can also turn Heat Pump Balance off entirely and adjust your AUX lockout temperature yourself. The AUX lockout temperature can be changed in SETTINGS > EQUIPMENT > HEAT PUMP.

There might be something wrong with your heat pump.

It could also be that there is something wrong with your heat pump. IE, it is running and using some energy but not generating any heat. Eventually, this will lead to the thermostat switching on the emergency electric heat and that will use even more power. Call an hvac specialist and have it inspected.

Where to find the specifications

Listed on the furnace

Somewhere inside the service panel of the furnace, there should be a schematic for the furnace. This may list the electrical specifications of the blower motor. If not, the blower motor itself will have a label on it. It should list the voltage, amperage, horsepower, etc.

Using an Ammeter

An ammeter is used to measure the amount of current flowing through an electrical circuit. You can use a clamp on ammeter to measure the amount of current being used by the blower motor while it's running.

Simply set the meter to measure current (A in the pictured meter), and clamp it on the hot wire feeding the motor.
_{This method may require working on or near live wires, please use caution and/or consult an expert to take the readings}

Calculate Usage

With the above information and Ohm's law, it's easy to determine how much power the motor will use over a given time period.

Ohm's law says that Power (P) = Voltage (V) x Current (I), so we can determine how much power the motor uses at a single instant in time.

ex.

P = 115V * 5.2A
P = 598 Watts

Next we have to determine how many kilowatt hours the motor will use, which we do by dividing by 1000.

P = 598 W / 1000
P = 0.598 kWh

So for every hour the motor runs, it will use 0.943 kilowatts of power.

Total power/day = 0.598kWh * 24h
Total power/day = 14.352kWh
Total power/month = 14.352Kwh * 30
Total power/month = 430.56kWh

Finally, if you multiply this number by the amount you pay per kilowatt hour. You'll see just about how much it costs to run the motor constantly.

Cost = 430.56kWh * $0.07
Cost = $30.14 per month

_Notes:
_{Results using this process will be an estimate only.}
_{Values used are not actual values, they are example values only.}
_{Calculations may be incorrect, nobody checked my math.}

Calculating total energy savings for LED lighting

That is fundamentally correct for the time the lights are on, yes. It will depend on the specific LEDs and ballasts chosen (the ballast may or may not be part of the fixture, and some cheesy outfits try to give the lumens per watt INTO the LED itself, ignoring the watts wasted in the ballast converting from AC to DC.)

@Tester101's "wire heating" strawman (in comment) would still be affected in the desirable direction (less amperage draw for same light = less wire heating), and is insignificant for any properly sized and constructed wiring regardless of light fixture choice.

Lumens per watt of LED fixtures vary widely, still, and there are definitely still fixtures for sale which seem to be built on the belief that buyers will see "LED" and think "very efficient" without actually delivering good efficiency (inefficient LEDs presumably being cheaper than efficient ones).